Abstract
The recent experimental developments in the measurement of hyperfine splittings in the bound states of charmonium and bottomonium are presented. Their implications for the hyperfine interactions in the heavy quark systems are discussed.
Highlights
The richness of the spectra of the excited states of atoms as well as hadrons lies in the principal quantum number and angular momentum dependence of the states, but in the spin–dependent multiplicities. These arise from spin–orbit, tensor, and spin–spin interactions between the constituents
The most interesting is the hyperfine structure that arises due to the magnetic interactions between the spins, which causes the splitting between spin–singlet (s1 + s2 = s = 0) and spin–triplet (s1 + s2 = s = 1) states
We reported observation in KS Kπ decay with 61+−1195 events and M(η′c) = 3642.9 ± 3.4 MeV, and ∆Mh f (2S )cc = 43.1 ± 3.4 [7]
Summary
The richness of the spectra of the excited states of atoms as well as hadrons lies in the principal quantum number and angular momentum dependence of the states, but in the spin–dependent multiplicities. These arise from spin–orbit, tensor, and spin–spin interactions between the constituents. The ground state singlet masses of mesons made up of two quarks are given by It is remarkable how well this textbook prediction works with the rather realistic assumption about the strong coupling constant αS (u, d) = 0.6, αS (u, d, s) = 0.4, αS (c) = 0.32, αS (b) = 0.18, and that |ψ(0)|2/m1m2 is a constant, = 33.
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